, developed by Conversition Strategies, gathers recent tweets about whatever search term the user has entered, evaluating those tweets for positive and negative "feelings".
TweetFeel monitors a large set of indicators, including keywords such as "love", "hate", or "sucks" and presents a stream of tweets with the search terms, and a tally of positive or negative sentiments, shown as happy or frowning face icons.
Users can search for any word of their choice, including specific things such as brands, products, and companies, or generic items such as cookies and football.
For example, a search for "Gordon Brown" revealed 54% of the related tweets were negative, including "Why is Gordon Brown still prime minister and why is Labour still in power? Why do we let them keep on digging the hole that will swallow us?".
However, another tweet, which read "Gordon Brown wins tonight, but he's lost" counted in the positive stream, but included a link to a scathing blog post about the prime minister.
Conversition said 100% accuracy is an "impossible goal" but its method has allowed TweetFeel to boast a level of accuracy that is higher and more comprehensive than other similar free services.
Meanwhile, Twitter use continues to grow in the US. ComScore said the website attracted 20.1m users in June, up 14% from May when it had 17m visitors, only 3.5% growth from April.
The website currently attracts more than 35m users worldwide every month.